Crops and soils Soils 18 Soil science 16 Plant-soil relationships 14 Soil management 12 Crops 11 Nutrition 11 more ... Congresses 10 Fertilizers 9 Soil fertility 7 Crops and climate 4 Environmental aspects 4 Rice 4 Corn 3 Heavy metal content 3 Nitrogen content 3 Plants 3 Research 3 Roots (Botany) 3 Soil erosion 3 Soil physics 3 Urea as fertilizer 3 Ammonia 2 Analysis 2 Crop yields 2 Encyclopedias 2 Humus 2 Mathematical models 2 Microorganisms 2 Nitrogen fertilizers 2 less ...